The present invention relates to a surface inspection apparatus and a surface inspection method for inspection in objects, for example, such as foreign matter, scratches, or COP (Crystal Defect) on the surface of a wafer and other inspected objects.
In the prior art, foreign matters on the surface of an inspected object have been measured by placing a luminous flux incident in the form of high incidence or low incidence on the surface of an inspected object.
However, with the trend of higher sensitivity of the inspection apparatus and fineness of steps, in the conventional surface inspection apparatus and the surface inspection method, for example, in a Bare-Si, it has been impossible to correctly separate the grow-in defect (fine crystal defect) on the surface or extremely thin foreign matter of residual matter caused by the surface polishing from the conventional foreign matter to measure them.
There has been proposed an example in which data of a measuring apparatus on the high incident side and data of a measuring apparatus on the low incident side are superposed, and from comparison therebetween, the inspection object is discriminated from the foreign matter.
It has been impossible to separate the conventional foreign matter or thin crystal defect from extremely fine foreign matter which is a residual matter caused by the surface polishing step to detect them.
With the trend of higher sensitivity of the inspection and fineness of steps, particularly in a Bare-Si, it has been desired to correctly separate the grow-in defect (fine crystal defect) on the surface or extremely thin foreign matter of residual matter caused by the surface polishing from the conventional foreign matter to measure them.
Further, it has been desired apparatus and method for separating micro scratches or slurries caused by CMP (Chemical Mechanical Process) that cannot be avoided in the fineness art to detect them with high sensitivity.
It is an object of the present invention to provide a surface inspection method and a surface inspection apparatus in which at least two different luminous fluxes are incident at different angles, scattered light of not less than two luminous fluxes incident at respective angles are separated by wavelength or polarized light, and the inspection object is discriminated on the basis of the scattering strength of the respective scattered light and the range of the scattered light.
It is a further object of the present invention to provide a surface inspection apparatus and a surface inspection method in which two different luminous fluxes are incident at different angles, scattered light of luminous fluxes incident at respective angles are separated by wavelength or polarized light, and the inspection object is discriminated on the basis of the scattering strength of the respective scattered light and the range of the scattered light and according to the kind of inspected objects.
The present invention relates to an improvement in a surface inspection apparatus and a surface inspection method for inspection objects, for example, such as foreign matter, scratches, or COP (crystal defect) on the surface of a wafer and other inspected objects.
According to one mode of the present invention, the surface inspection apparatus comprises a light source section for emitting a first luminous flux having a first characteristic and a second luminous flux having a second characteristic; a first irradiation optical system in which the first luminous flux is irradiated on the surface of an inspected object at a first irradiation angle; a second irradiation optical system in which the second luminous flux is irradiated on the surface of an inspected object at a second irradiation angle; a light receiving optical system for receiving the scattered light of the first luminous flux irradiated by the first irradiation optical system and generated from the inspection object on the surface of an inspected object and the scattered light of the second luminous flux irradiated by the second irradiation optical system and generated from the inspection object on the surface of an inspected object; a first light receiving section for converting the scattered light of the first luminous flux received by the light receiving optical system into a first light receiving signal; a second light receiving section for converting the scattered light of the second luminous flux received by the light receiving optical system into a second light receiving signal; a displacement section for relatively displacing an inspected object and an irradiation luminous flux of the irradiation optical system; and a discrimination section for discriminating the kind of the inspection object on an inspected object on the basis of the strength of scattered light of the first and second light receiving signals and the scattered range of the scattered light of the first and second light receiving signals.
Preferably, the first characteristic of the first luminous flux and the second characteristic of the second luminous flux emitted from the light source section are a wavelength of luminous flux or a polarized light component. The first irradiation angle of the first irradiation optical system is set to be smaller than the second irradiation angle of the second irradiation optical system.
Preferably, the discrimination section carries out the process of scattered light quantity ratio for obtaining the strength ratio of the scattered light of the first and second light receiving signals, and the process of scattered range detection for obtaining the scattered range of scattered light according to whether or not the first and second light receiving signals are at a level above a predetermined level. Further, the discrimination section carries out the discrimination processes as described below every position of the surface of an inspected object:
(A) When judgment is made that the scattered light generated from the inspection object is present in only one of either the first light receiving signal or the second light receiving signal, the first discrimination process for discriminating that the kind of the inspection object is a first inspection object is carried out.
(B) When judgment is made that the scattered light generated from the inspection object is present in both the first light receiving signal and the second light receiving signal, the ratio between the strength of scattered light of the first light receiving signal and the strength of scattered light of the second light receiving signal is obtained, and if the ratio is at a level above a predetermined level, the second discrimination process for discriminating that the kind of the inspection object is a second inspection object is carried out.
(C) When judgment is made that the scattered light generated from the inspection object is present in both the first light receiving signal and the second light receiving signal, the ratio between the strength of scattered light of the first light receiving signal and the strength of scattered light of the second light receiving signal is obtained, and the ratio is at a level above a predetermined level, and further, a first function due to the strength of scattered light and the scattered range of scattered light of the first light receiving signal and a second function due to the strength of scattered light and the scattered range of scattered light of the second light receiving signal are obtained, and when the ratio therebetween is at a value above a predetermined value, the discrimination process for discriminating that the kind of the inspection object is a third inspection object is carried out.
(D) When judgment is made that scattered light generated from the inspection object not falling under the process is present in the first light receiving signal or the second light receiving signal, the discrimination process for discriminating that the kind of the inspection object is normal foreign matter is carried out.
Preferably, the kind of the inspection object discriminated by the discrimination section is decided according to the kind of the inspected object.
For example, where the inspected object is a bare semiconductor wafer (Bare-Si), the discrimination section discriminates that the first inspection object is COP (crystal defect) by the first discrimination process; that the second inspection object is COP (crystal defect) by the second discrimination process; and that the third inspection object is extremely thin foreign matter by the third discrimination process.
Further, preferably, where the inspected object is a semiconductor wafer after CMP (chemical mechanical process) process of a wafer with a membrane, the discrimination section discriminates that the first foreign matter is COP (crystal defect) by the first discrimination process; that the second foreign matter is micro scratch by the second discrimination process; and that the third foreign matter is micro scratch by the third discrimination process.